The present invention relates to implantable articles and methods of for implanting such articles. More particularly the invention relates to a bone prosthesis, prosthesis trial, instrument and method for implanting the same.
There are known to exist many designs for and methods for implanting implantable articles, such as bone prostheses. Such bone prostheses include components of artificial joints, such as elbows, hips, knees and shoulders.
One such implantable prosthesis is a shoulder prosthesis. During the life time of a patient, it may be necessary to perform a total shoulder replacement procedure on a patient as a result of, for example, disease or trauma, for example disease from osteoarthritis or rheumatoid arthritis. Currently, most implantable shoulder prostheses are total shoulder prostheses. In a total shoulder replacement procedure, a humeral component having a head portion is utilized to replace the natural head portion of the upper arm bone or humerus. The humeral component typically has an elongated intermedullary stem, which is utilized to secure the humeral component to the patient's humerus. In such a total shoulder replacement procedure, the natural glenoid surface of the scapula is resurfaced or otherwise replaced with a glenoid component that provides a bearing surface for the head portion of the humeral component.
With the average age of patients requiring shoulder arthroplasty surgery decreasing, orthopaedic implant manufacturers are developing “bone-sparing” implants for the initial treatment of the degenerative arthritis. While bone-sparing implants for the treatment hip and knee arthroplasty are becoming quite common, bone-sparing shoulder arthroplasty techniques and prostheses are also being developed.
Shoulder surface replacement prostheses are being developed to replace the articulating surface of the proximal humerus with a minimal bone resection and minimal disruption of the metaphysis and the diaphysis. Current designs use a semi-spherical articular dome with a small stem for rotational stability. The under surface of the articular head is also semi-spherical and meets with a spherically machined humeral.
Typically, however, arthritis of the gleno-humeral joint causes flattening of the humeral head with a large medial osteophyte. The flat humeral head can cause voids in the bone under the prosthesis resulting in limited contact between the prosthesis and the resected bone and may limit the load transfer capability between the prosthesis and the humerus. During a surface replacement procedure, it may be necessary to remove the initial implant once seated because of incorrect sizing. The correct sizing may be determined, for example, during the trialing of an implant. Prior art attempts at removing the implant have resulted in the damage of the surrounding bone during the removal of the implant.
Alternatively, a surface replacement implant may need to be revised where damage has occurred to surface replacement implant or to the corresponding gleniod component. During such a replacement procedure the initial implant will need to be extracted. Extraction of the initial implant may be made more difficult if the initial implant includes a porous coating to promote bony in-growth. The bony in-growth of the surface implant stem may make the removal of the surface replacement prosthesis extremely difficult.
Due to the nature of the progression of the aging or disease of the joint caused by, for example, osteoarthritis, or due to prosthesis wear it may be necessary to revise or replace the surface replacement prosthesis with a total joint prosthesis. The surface replacement prosthesis must be removed from the bone so that bone may be resected.
Prior art procedures for the removal of the surface replacement prostheses have been limited to the use of an osteotome and a mallet to wedge the implant from under the outer lip of the implant and free the implant from the bone underneath the implant.
The removal of the implant from the bone using an osteotome and a wedge is wrought with many problems including damage to the bone around the implant and generally difficulty in removal of the implant. The present invention is intended to resolve at least some of the aforementioned problems.